Answered

If y = 3x^3 - 2x and dx/dt equals 3, find dy/dt when x = -2. Give only the numerical answer. For example, if dy, dt = 4, type only 4.

Answer :

Answer:

 [tex]\frac{dy}{dt} = 102[/tex]

Step-by-step explanation:

step(i)

Given function y = 3 x³ - 2 x  ... (i)

Differentiating equation (i) with respective to 'x'

    [tex]\frac{dy}{dx} = 3 (3 x^{2} ) - 2(1)[/tex]

Given x = -2

[tex](\frac{dy}{dx} ) x_{=-2} = 3 (3 (-2)^{2} ) - 2(1)[/tex]

[tex](\frac{dy}{dx} ) x_{=-2} = 36 -2 =34[/tex]

Step(ii):-

we know that

                     [tex]\frac{dy}{dx} = \frac{\frac{dy}{dt} }{\frac{dx}{dt} }[/tex]

Given    [tex]\frac{dx}{dt} = 3 and \frac{dy}{dx} = 34[/tex]

                  [tex]\frac{dy}{dx} = \frac{\frac{dy}{dt} }{\frac{dx}{dt} }[/tex]

substitute values    [tex]\frac{dx}{dt} = 3 and \frac{dy}{dx} = 34[/tex]  

           ⇒        [tex]34 = \frac{\frac{dy}{dt} }{3 }[/tex]

cross multiplication , we get

                      [tex]\frac{dy}{dt} = 34( 3 ) = 102[/tex]

Final answer:-

 [tex]\frac{dy}{dt} = 34( 3 ) = 102[/tex]

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